Emit less compiler optimization remarks in samplepgo to reduce a call to...

Emit less compiler optimization remarks in samplepgo to reduce a call to findCalleeFunctionSamples which is going to be refactored.

Summary: Now the SamplePGO support is more stable, we do not need so many verbose optimization remarks emitted.

Reviewers: dnovillo, davidxl

Reviewed By: davidxl

Subscribers: fhahn, llvm-commits

Differential Revision: https://reviews.llvm.org/D31826

llvm-svn: 299883